The Clinical Epilepsy Section has been developing and testing new techniques to achieve improved seizure control, reduce drug-induced side effects, and achieve better rehabilitation in patients with severe epilepsy. These include simultaneous video and telemetered EEG recording of seizures, daily determinations of antiepileptic drug serum concentrations, and most recently, the concomitant use of positron emission tomography. Patients with very long histories of uncontrolled seizures are admitted for a complete evaluation, including all basic neurologic studies and daily objective toxicity battery. Intensive monitoring techniques are used to establish a seizure diagnosis, which is then utilized to design an appropriate therapeutic regimen for each patient. The study of positron emission computerized tomography (PECT) in patients with localized brain lesions has demonstrated focal hypometabolic cerebral areas corresponding to the interictal seizure EEG focus. Such studies allow more definitive overall identification of the localization of the epileptic lesion and suggest new avenues of investigation into the basic mechanism of the epilepsies.